PURPOSE: To realize a constrained logic programming (CLP) processing system having a higher-order interchangeability with a prolog processing system by executing the mixture of a CLP program and a prolog program.

CONSTITUTION: A CLP source program 103 is converted to a prolog program in a conversion processing part 101 by a user indication 107 from a television picture 105, and this program is stored in an internal memory 106. A prolog source program 104 is inputted by a prolog input processing 112, and its form is converted to an internal form, and this program is stored in the internal memory. The prolog function part of a conversion processing 111 is converted to a program 121, and the constrained processing part is so converted that a constrained processing predicate 123 is called. Execution is started in a program execution processing 102 by a user indication from the television picture, and the prolog processing system is used to execute the program 106. Thus, the CLP program and the prolog program are permitted to exist together, and the CLP processing system having a higher-order interchangeability with the conventional prolog processing system is realized.